He called it the second most important job he could ever hold, and as Gordon Brown walked away from it last week – leaving Downing Street hand in hand with his two grinning little boys – the impression was of a man now tackling anew his first job: that of husband and father. But is it possible to do both well? Can a man – or, indeed, a woman – succeed in high office and still be there (even occasionally) for high tea? Or is the price of power inevitably abdication from family life?

For an election that for the first time pitched three fathers of pre-school children against each other for the crown, there has been oddly little discussion of the tensions between fatherhood and politics.

The wives and their working lives were scrutinised to death, with endless debate over the merits of Miriam González Durántez's refusal to take a month off work to campaign for her husband, Nick Clegg: but not for the first time, the men's domestic credentials have escaped largely unscathed.

Yet the rise of Cameron and Clegg represents a pivotal moment for fathers and how they navigate their family lives in government matters. For they embody a pioneer generation of men, mostly under 45, who have tried to forge a very different relationship with their children than that of the previous generation.

Westminster culture isn't quite as toxic to parenthood as it was during the days when "spending more time with the family" was a euphemism for resigning in disgrace. Tony Blair was famous for his solicitousness towards ministerial parents and private kindness towards some of their teenage children. Yet Alastair Campbell's diaries, which skimped on the rows between Blair and Brown but unsparingly chronicled the furious exchanges between himself and his partner, Fiona – nearly all about the way his 24/7 workaholic life in No 10 was damaging their family life – is an honest portrait of the inevitable pressures at the top.

As political editor of the Observer, I have some reason to know how it felt: when my own son was two I resigned, worried that family life had become stretched to the limit by my job. The great surprise was how many men, as well as women, at Westminster secretly harboured the same fears: I heard heartfelt and guilty stories, from cabinet level down to the backroom boys, from male politicians afraid of missing out on their children's lives. But then, like Cameron and Clegg, most of these were from a new generation – one that grew up taking it for granted that women would have a life outside the home, and saw the balance of domestic power shift accordingly.

Both the Conservative and Liberal Democrat leaders married women with high-powered careers: their wives were the major breadwinners during the years in opposition, and both men have willingly accepted their fair share of the load at home.

Until the election, Clegg usually did the school run – he could be spared more easily from Westminster than Miriam could from her law firm – while Samantha Cameron insisted that her husband be home to do bathtime at least once a week. Tony Blair may have been a deeply committed parent, but Cherie often pointed out that he barely knew how to work the washing machine. By contrast, these two are poster boys for a new and more equal kind of working parenthood.

But can it survive the transition to No 10? When Brown moved in, it wasn't such a shock to his family life: he has always worked round the clock, and Sarah had already given up the PR agency she co-founded, partly to hold the family together.

In some ways, things were easier at Downing Street than at the Treasury, with the family living above the shop and the boys coming downstairs for quick visits during the day (state visitors to Downing Street during the Blair era quickly got used to Leo, as a toddler, wandering into meetings: you would sometimes find bits of train set on Brown's office carpets).

But for the Camerons and the Cleggs, it will undeniably be a brutal gear change. The biggest challenge for fathers in Whitehall is the same as for any working parent: time. The life of a prime minister is not conducive to, well, much of a life: there are calls round the clock, gruelling international trips, pressure so intense that – as Brown put it in his resignation speech – only those who have been there can really understand it.

Holidays are nothing of the sort, with red boxes still delivered to the poolside and destinations governed by the ease of getting a secure phone line.

Blair dithered for months over whether to take paternity leave when Leo was born, fearing it would be seen as a dereliction of duty, and eventually settled for the worst of both worlds by retiring to Chequers for a break but spending much of it working. Cameron will face the same choice when his fourth child is born later this year, perhaps at a time of national strife as the economic crisis works its way through.

And unlike most working parents, prime ministerial fathers must watch their children growing up in the media spotlight. When I interviewed Cameron shortly after he became Tory leader in 2005, he admitted he and Samantha already clashed at times over how much to expose the children – he tends to tell anecdotes about them in public; she worries more about their privacy. There will be more such moments in the years to come.

Will these two fathers cope? There is more than their own family lives riding on it: with a little honesty from the top, this could be the beginning of a new national conversation about working fatherhood – perhaps even the end of an unhealthy obssession with working motherhood. Now there's a political legacy.

• This article was amended on 15 May 2010. The original article stated that the Camerons were expecting a third child this year. The child will be their fourth, after son Ivan, who had cerebral palsy and epilepsy, died in February last year, at the age of six. We also referred to the Liberal Democrat leader's wife as Miriam Clegg. Her name is Miriam González Durántez. These errors have been corrected.